1. Field of the Invention
The present invention relates to an image forming apparatus, function extending method and user authentication system. The present invention more specifically relates to a technique of extending available function by executing user authentication.
2. Description of the Background Art
In recent years, in image forming apparatuses called as complex devices or MFPs (multifunction peripherals), setting authorities to use any functions may be set for each user in advance. This kind of authority settings of each user is implemented from the perspective of cost management and/or prevention of leakage of information. For example, color image formation which requires toner of multiple hues is generally more costly to be performed than image formation with a toner of a single color. If users who are able to make color copy and/or color printing are restricted, increase in the cost may be controlled. Moreover, in case of making data transmission from the image forming apparatus to an external device, addresses to be selected as destinations are limited for each user, thereby curbing the leakage of information. This type of image forming apparatus executes user authentication when it is to be used. If a user is successfully authenticated, the image forming apparatus transits to a logged-in state in which the authenticated user is logging. In the logged-in state, functions corresponding to authority of the authenticated user are available in the image forming apparatus. When job is executed based on the authenticated user's instructions, job execution history is recorded as log.
According to a conventional technique for executing user authentication as described above, two-staged authorities which are standard authority to use standard functions, and additional authority to use additional functions are set in advance for a user. When a function that the user is trying to use is contained in the additional functions, additional authentication for changing authority to additional authority is executed after executing authentication for using standard functions with standard authority. This technique is disclosed, for example in Japanese patent application laid-open No. 2007-156698. According to the conventional technique, by executing two-staged authentication, unauthorized use by third parties is prevented. As an example, an administrator who has a broad range of use authority leaves from the image forming apparatus after he or she performs user authentication. In this case, unauthorized use of the image forming apparatus with management authority by third parties is prevented.
The two-staged authentication as described above is for a user to make additional functions set for oneself available. So, if a function that the user would like to use is not contained in additional functions which are available with additional authority, the user cannot use the function that he or she would like to use. For instance, in order to limit the use of costly functions such as color copy or color printing by ordinary users, authority to use functions such as color copy or color printing is not contained in standard authority or additional authority set for ordinary users. So, functions such as color copy or color printing are not available for ordinary users even if two-staged authentication is performed.
According to a technique conventionally used as described above, it is assumed that an ordinary user cannot make color copy even if the ordinary user is requested to make a color copy by his or her supervisor. So, the ordinary user requested to make a color copy needs to ask another user who has authority to make color copy for executing the job. If the ordinary user has already logged into the image forming apparatus, he or she needs to perform a log out operation in order for another user to use the image forming apparatus, resulting in cumbersome operations and user-unfriendliness. Also, when job is executed in the image forming apparatus, log is recorded as a job execution history of a logged-in user. Therefore accurate charging control is not executed in above-described case.
Where a user who is unauthorized to make color copy is requested to make a color copy by his or her supervisor as explained above, the function is preferably made temporary available for the requested user while he or she remains logging into the image forming apparatus.